Interpretive Summary: Limited information concerning chicken immunity and immune system hinders rapid progress in the development novel control strategy against many poultry diseases. In this paper, ARS scientists describe the molecular cloning and functional analysis of an important chicken cytokine which is secreted by activated chicken T-lymphocytes. This cytokine is homologous to mammalian Interleukin-17 (IL-17) and plays an important role during inflammatory response following infection. ARS scientists describe its importance in avian immune development for the first time and ability to develop recombinant chicken IL-17 will enhance the understanding of avian immunity to pathogens and facilitate the development of novel control methods for many poultry pathogens

Technical Abstract:
IL-17 is a proinflammatory cytokine produced by activated T cells. A 917 bp cDNA encoding the IL-17 gene was isolated from our EST cDNA library prepared from intestinal intraepithelial lymphocytes (IELs) of Eimeria-infected chicken. It contained a 507 bp open reading frame predicted to encode a protein of 169 amino acids with a molecular mass of 18.9 kDa, a 27 residue NH2-terminal signal peptide, a single potential N-linked glycosylation site, and 6 cysteine residues conserved with mammalian IL-17s. Chicken IL-17 shared 37-46% amino acid sequence identity to the previously described mammalian homologues and also was homologous to the open reading frame 132 of Herpesvirus saimiri (HVS 13). By Northern blot analysis, IL-17 transcripts were identified in a reticulendotheliosis virus-transformed chicken lymphoblast cell line (CU205) and Con A-stimulated splenic lymphocytes but not other chicken cell lines or normal tissues. Conditioned medium from COS-7 cells transfected with chicken IL-17 cDNA induced IL-6 production by chicken embryonic fibroblasts suggesting a functional role for the cytokine in avian immunity.